Gilt Selection Sow Longevity

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Gilt Selection Sow Longevity

• An S 225
• Fall 2009

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Why should we be concerned with longevity?

• Performance differences
• Number born alive
• Litter weaning weight
• Grow Finish Performance
• Better protection from disease??
• Introduction of more gilts associated costs
• Welfare issue

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Reasons For Culling
Reason
Percentage Culled

• Reproductive failure 30 - 35
• Old age 15
  - 20
• Performance 15 - 20
• Feet and leg problems 10 - 15
• Death 5
  - 10
• Post-farrowing problems 3 - 5
• Other
  5 - 10

Source Stalder, ISU
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Reason for sow removal within the reproductive
failure category

• Reason Percentage
  Culled
• Did not conceive 40 - 50
• Pregnancy check negative 15 - 20
• Fail to farrow 20 -
  30
• Aborted 5 - 15
• Other 0
  - 5

Source Stalder, ISU
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Cost of Replacing a Sow

• Replacement gilt
• Facility, feed, and labor during isolation and
  acclimation
• Vaccination and other veterinary expenses
• Disease risk
• Opportunity cost (interest rate)
• Performance difference between a gilt and mature
  sow

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Factors Influencing Sow Longevity

• Host of management effects
• Feed intake, lactation length, gestation housing,
  etc.
• Factors under some genetic control
• Backfat of gilt at selection affects sow longevity

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Risk Factors Associated with Poor Longevity

• Primary factors
• Genetics
• Gilt Development
• Feet and Leg Soundness
• Lactation Length
• Body Condition

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Risk Factors Associated with Poor Longevity

• Secondary factors
• Repeat Breeding
• Seasonal Variation
• Sow Housing
• Caretaker Skills and Management

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Relationship of Sow Longevity and Backfat,
Brisbane Chenais, 1997

• Evaluated longevity in purebred Yorkshire and
  Landrace herds where backfat was measured on
  replacement gilts.
• Divided the gilts into 3 backfat categories.
• Leanest - lt 10 mm (.40 in.)
• Intermediate - 10 to 18 mm (.40 to .70 in.)
• Fattest - gt 18 mm (.70 in.)
• Strong negative association between leanness and
  longevity.

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Sow Housing

• Sows in the U.S. are predominantly housed in
  gestation (62) and farrowing (84) stalls
• Ease of management
• Reduced aggression
• Individual care and attention
• Difficult to determine the association between
  sow housing systems and longevity

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Sow Housing

• Improved sow longevity does not appear to be
  necessarily associated with sows housed in
  individual stalls or grouped in pens during
  gestation
• Small group housing has been shown to be
  successful in some systems
• Sows in outdoor production systems have been
  shown to have higher mortality rates when
  compared to indoor production systems

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Evaluation of a Group of Replacement Gilt
Candidates

• Be sure to evaluate replacement gilts in groups
  of 10 to 20
• Evaluation should occur in a place where various
  traits can be easily observed and where
  locomotion can be adequately viewed!

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Evaluation of a Group of Replacement Gilt
Candidates

• Do not rely on memory to record all traits for
  the gilts evaluated
• Develop a scoring sheet to use in the evaluation
  process

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Selection for Soundness

• Feet and leg problems are one of the biggest
  reasons females are culled
• Screen gilts before they enter the herd
• Visual appraisal can identify replacements with
  problems that may affect longevity
• Conformation
• Structural soundness
• Feet and leg abnormalities
• Injuries

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Gilt Selection Criteria
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Ideal Replacement Gilt

• Big feet, big toes
• Evenly sized toes that are spread apart
• Good flex to her pasterns

• Adequate base width front and rear
• Balanced, level design
• Loose structured

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Structure Evaluation
Good base width
Width of chest, foot size
Level structure, good hip structure
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Evaluate Front Structure

• Angle M (between humerus and radius) should be
  less than 90
• More cushion and ease of movement
• Straight-fronted
• Shoulder too far forward
• More susceptible to injuries

Desirable
Undesirable
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Correct Skeletal Structure

• Cushion and flex to the joints
• Walks fluidly
• Less susceptible to stiff joints and arthritis
• Results in longer time in herd

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Weak Pasterns

• Soft or weak pasterns
• Have a shock absorbing effect
• Positive impact on longevity if remaining
  structure is correct
• Avoid severe cases

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Front Leg Side View
Buck-kneed
Normal
Soft Pasterns
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Front View Abnormalities
Splay Footed
Pigeon-toed
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Evaluate Feet and Toes

• Ideal toes are big, evenly sized, and spread
  apart
• Better weight distribution
• Small inside toes
• Greater risk of cracked hooves and foot pad
  lesions
• Uneven toe size affects mobility

Ideal
Undesirable
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Evaluate Feet and Toes

• Small toes and feet are undesirable
• Weight is concentrated in a smaller area
• Injuries are costly and can be difficult to
  identify
• Treat and retain with caution
• Injuries are not genetically related

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Evaluate Rear Leg Structure

• Angle N (between femur and tibia) is less than in
  bottom picture
• More cushion and ease of movement
• Hip, stifle, and hock are in straight line
• High top, steep rump, post legged
• More susceptible to injuries and lameness

Desirable
Undesirable
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Rear Leg Structure

• Straight pasterns
• Straight hip and steep rump
• Difficulty getting up and lying down
• Sickle hocked
• More trouble getting up and down in confinement

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Rear Leg Side View
Normal
Sickle-hocked
Post-legged
Soft pasterns
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Rear View Cow-hocked
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Other Considerations

• Narrow based gilts should be culled
• Tight muscled, goose-stepping gilts should be
  culled

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Examples ofGilts to Cull
Steep rumped, shallow bodied
Undesirable rear leg structure
Straight fronted, broken topped
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Other Factors Affecting Soundness

• Disease organisms that may cause arthritic
  conditions
• Floor surface
• Rough floors, slats with sharp edges, smooth wet
  floors
• Nutritional deficiencies
• Calcium, phosphorus, zinc, biotin, etc.

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Reproductive Soundness -- Underlines

• An ideal underline should have seven or more
  functional nipples on each side.
• The nipples should be well spaced and well
  developed.
• Blind or pin nipples should not be present.

Acceptable
Unacceptable
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Reproductive Soundness -- External Genitalia
Tipped Vulva
Small Vulva
Infantile Vulva
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Additional Criteria for Selection

• Growth
• Top 50-60 of contemporary group
• Avoid slow growing gilts
• Backfat may be farm-specific
• Recommendations may change due to genetics,
  environment, end market

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Avoid Genetic Defects
Hermaphrodite
Polydactyl feet
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Systematic process for evaluating reproductive
and leg soundness in replacement gilt candidates
Thirdly, Evaluate top shape, rib shape, body
depth and width, etc. where variation and only
extremes are most critical
Ending Point
Start Here
Secondly, evaluate feet and legs next, some
traits are considered all or nothing traits, and
others require decisions by the producer.
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Summary

• Structural correct females have improved
  longevity
• Whether purchased or raised, careful screening of
  replacements is essential
• Careful evaluation of candidates for replacement
  reduces culling later on
• Structural soundness should be viewed as all or
  none

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Take Home Messages

• Stress Gilt Development to Improve Longevity
• Soundness
• Structural and Reproductive
• Purchased Gilts
• Internal Multiplication Systems
• Early age at puberty
• Avoid selecting extremely lean gilts
• Plan for having plenty of replacement gilts when
  they are most commonly needed

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